1. Technical Field
The present invention relates generally to aircraft control, and more particularly, to methods and apparatus for displaying aircraft status.
2. Background Art and Technical Problems
Vehicle Control Systems (VCSs) have significantly improved safety, precision, and efficiency of travel. These improvements are due in part to the VCS automating tasks that were previously performed by the vehicle operator. However, while the VCS can provide efficient and optimal control, the vehicle operator is preferably provided with accurate and timely information to monitor vehicle behavior and direct overall vehicle operations. As the accuracy and frequency of information provided to the operator is improved, the operator is better able to make informed decisions, resulting in improved vehicle performance.
One example of a VCS is an aircraft Flight Control System (FCS). A FCS may complete all major tasks associated with flying an aircraft from origin to destination, including flight planning, guidance, control, and navigation. This reduces flight crew workload, improves mission safety, and increases the economy of aircraft operation. However, while these advantages are provided by the FCS, various operational and training issues have been raised, including, but not limited to: discrepancies between a pilot's understanding of the avionics design and actual operation; over-emphasis on the training of required operating procedures and under-emphasis on presenting a model of the actual organization and operation of the avionics system; and the quality and quantity of information presented to the pilot on the avionics displays. These issues are not surprising when the complexity of a FCS is considered in relation to the form and content of the information that is displayed to the flight crew.
For example, consider a Vertical Guidance Component (VGC) 100 of an FCS as shown in FIG. 1. The VGC 100 suitably maintains a selected vertical profile, for example, by adjusting the pitch of an elevator 102 and thrust of an engine 112 with control signals received from an autopilot 108 and autothrottle 118. The autothrottle 118 and autopilot 108 may receive manual instructions from the flight crew through the Mode Control Panel (MCP) 120.
Alternatively, the flight crew may opt to have a Flight Management System (FMS) 110 automatically select pitch modes, attitude targets, thrust modes and/or speed targets. The FMS 110 implements processes and decision-making algorithms which automate various tasks, such as control of pitch, roll, thrust mode selection (i.e., Vertical Navigation (VNAV)), altitude, heading, track, and speed target selection (i.e., FMS SPDS). The processes and decision-making algorithms utilize hundreds of rules and considerations relating to navigation, airspace regulations, aircraft operational limits, and the like, to select the appropriate modes and targets of flight. Once the FMS 110 has selected the appropriate control modes and targets of flight, display signals 122 representing the control signals transmitted to the autopilot and autothrottle are provided to a Flight Mode Annunciator (FMA) 300 of a primary flight display 114 for review by the flight crew.
The FMA 300 typically includes three panels: an autothrottle (speed) display panel 116, a roll autopilot display panel 118, and a pitch (altitude) autopilot display panel 120. Referring to FIG. 2, the autothrottle display panel 116 annunciates a speed target 302 and a speed control mode 304, the roll autopilot display panel 118 presents a heading/track target 306 and a heading/track control mode 308, and the altitude autothrottle display panel 120 provides an altitude target 310 and an altitude control mode 312. While these panels may be used by the pilot to determine the current behavior of the aircraft, a significant amount of interpretation remains to specifically identify the current objectives of the aircraft control system. This interpretation problem is exacerbated because some combinations of annunciations are not exclusive to particular modes of flight. For example, the annunciations PITCH and IDLE are used as the annunciation combination for no less than three separate aircraft behaviors. In addition, even after the pilot has interpreted the general behavior, behavior specifics may be unascertainable from the display.
To illustrate, if the pilot has determined the aircraft is in descent, no information is presented as to the purpose or objective of the descent, such as whether the aircraft is in EARLY DESCENT or LATE DESCENT. To determine the exact type of descent, the pilot typically accesses a performance page on a Control Display Unit (CDU) and monitors the path error information, which usually demands the pilot's attention for a substantial period of time.
Due to the large number of processes and algorithms used by VGCs 100, the limited number of targets and outputs displayed for the flight crew on conventional FMAs 300 within the user display interface 130, and the complexity and amount of information that is displayed in the cockpit in addition to the targets and outputs on FMA 300, the flight-crew can lose track of the VGC's 100 intentions and behavior (e.g. climb, cruise, descent, etc.). Furthermore, subtle differences in modes and mode transitions may go unnoticed by the flight crew, the flight crew may incorrectly interpret the system's actions as being inconsistent with expected conduct (i.e. automation surprise), and less than optimal adjustments may be made by the flight crew based upon an incorrect understanding of the system operation.